Free piston engine



N 1965 R. A. ROBERTSON 3,170,

FREE PISTON ENGINE Filed Nov. 28, 1962 4 Sheets-Sheet 1 IN VENTOR. 1P9 mm A. foeeymou A rroplysvs 4 Sheets-Sheet 2 Filed Nov. 28, 1962 IN VEN TOR. fan-ram ,4. fies/77:50

(Anya-A A77'DP/YEY Feb. 23, 1965 R. A. ROBERTSON FREE PISTON ENGINE Filed Nov. 28, 1962 4 Sheets-Sheet 3 Kano w Afaaaersou Feb. 23, 1965 R. A. ROBERTSON 3,170,406

FREE PISTON ENGINE Filed Nov. 28, 1962 4 Sheets-Sheet 4 IN VEN TOR. lF/imowo A Yeas/e130 hydraulic pressure waves;

United" States Patent ice 3,170,406 FREE PISTON ENGINE Raymond A. Robertson, White Hill Road, RED. 1,

Yorktown Heights, NY. 7 Filed Nov. 28, 1962, Ser. No. 240,523 Claims. (Cl. 103-54) This invention relates to a free piston type engine and more' particularly to a free piston engine adapted to actuate a pumping device.

In prior art tree piston engines which have been adapted for pumping fluids, the pumping element or piston has customarily been either the end portion of the engine piston opposite the'end portion to which the operating forces are applied or a separate pump piston connected to the engine piston. In either of these arrangements, the engine and pump assembly lacks flexibility since the pump piston must necessarily have'the same rate and 'extent of movement as'that of the engine piston. Thus with the prior art arrangements, if the driving forces .for the engine piston are sufficiently in excess of the opposing forces of the fluid upon which the pump is acting, the engine piston will travel substantially throughout its entire stroke for each cycle of operation. Consequently, the prior art assembly is in eifect restricted to operate as a positive displacement pump in which the displacement is a constant.

The prior art arrangement of connecting the pump piston directly to' the engine piston or of making the pump piston integral with the engine piston necessarily limits the nature of the motion of the engine piston to be identicalto that of the pump piston. In many applications the pump may be acting upon a fluid of a viscous naturesuch as a liquid where the desired cycle of motion for the pump piston can be greatly different from gine piston initially experience a rapid movement in order that excessive gas pressures are not developed within the engine "chamber. At the same time wher the pump arrangement is handling a liquid it may be undesirable to .attempt'to set the liquid into motion in a very rapid manner since this can cause excessively high In many prior art free piston engine and pump ar--' rangements the returnforce for thejtree piston is derived from the fluid being pumped by the pump piston. Such an arrangement of. necessity requires various valves, accumulators, pressure regulators, and the like for the fluid being pumped in order to obtain the return force function. i 1

It is an object of the invention to provide an elastic coupling between, the engine piston and the means for v applyinga return force to it.

Another object of theinve'ntionis to providea means for elastically coupling a free piston to a load. Still another object ,of the invention is to provide means for elastically'transmitting force-from a free piston to a pumping device.

An additional object of the invention is to provide a free piston type engine which comprises a plurality of chambers having free pistons and in which eachof the tree pistons transmits. force to a load device through an elastic coupling.

A further object of the invention is to provide a free her to provide the return force to the .free' piston and means extending from the chamber for transmitting the g movement of the pistonto a load.

mans Patented Feb. 23, 1965 In one embodiment of the invention the free piston type device comprises a chamber having a piston therein. Means are provided for urging the piston to move in a predetermined direction within the chamber. There is also disposed within the chamber an additional piston spaced apart from the first piston. Means are disposed in the space between the pistons for elastically transmit- In still another embodiment of the invention the additional piston is provided with means for pumping a fluid.

In an'aditional embodiment ofthe invention the 'free piston type engine includes means for applying a pressure tluid to the piston to move it within the chamber in a predetermined direction and means .for releasing the fluid applied to the piston from the chamber aftermovement of the piston in a predetermined direction. This arrangement is used in conjunction with the additional piston construction.

In a further embodiment of the invention, a plurality of free engine pistons and one or more additional ,pis tons are-disposed in a common chamber.

In still a further embodiment of the invention the free piston type engine which is adapted to actuate a pump device or. the like by transmission of the movement of the piston from without the cylinder includes means disposed within the cylinder for urging the piston to move in the return direction.

return force to the free piston is disposed within the engine chamber;

FIG. 2 is a section view of a-horizontally opposed free piston type engine actuating a plurality of pumping devices and containing means within the chamber for applying return forces to each of the pistons;

FIG. 3 is a section View ofa free piston engine type device in which the engine piston acts through an elastic 7 coupling upon an additional pistonwhich is adapted to on additional piston which is centrally disposed therebetween and which includes pumping provisions; p i FIG. 'I is a perspective view of the additional centrally 1 disposed piston of thetype used in the embodiment shown piston type device which includes means within the chamtransmit force to a load and'to provide the return force :for the engine piston; FIG. 4 is'a section view of a free piston type device which includes horizontally opposed enginepistons as well as additional pistons having pumpingmembers;

FIG. Sis a section View of an embodiment of the invention in which the horizontally opposed pistons and additional pistons are disposed in separate chambers mechanically, connected to one another;

FIG. 6 is a section view in which: free pistons disposed in the end portions of a chamber are adapted to actuate in FIG. 6; and 1 FIG. 8 is a section View showing a schematic represem tation of means foractuating the combustion arrangement for horizontally opposed pistonsdisposed in a common chamber which includes additional pistons having pumpingmeans. v, g

As shown in FIG. 1 the free piston type engine which is adapted to transmit force from the free or engine piston to a load includes chamber 20 in which piston 21 is disposed. End 21a of the piston is exposed to the forces of a pressured fluid which move the piston to the right as shown in FIG. 1. End 21b of the piston, upon movement thereof, compresses fluid Within end portion 20a of the chamber. The interaction of end 21b with the fluid in the chamber serves as the means mechanically connected to the piston and elastically responsive to the movement thereof for urging the piston to move opposite to the direction of force applied by the pressured fluid to end 21a.

Pump piston 22 extending from free piston 21 moves within pump chamber 23. During movement of piston 21 to the right as seen in FIG. 1, pump piston 22 forces fluid from pump chamber 23 and through outlet passage 24 by way of check valve '25 to a receiver or the like for the pressured fluid. Upon movement of piston 21 to the left as shown in FIG. 1, the pump piston develops a relative negative pressure within the pump chamber which causes a flow of fluid through check valve 26 and into inlet passage 27. In FIG. 1 the arrows rep resent the direction of flow for each cycle of operation.

The means for applying a pressured fluid to the piston to move it in a predetermined direction, namely to the right in FIG. 1, can include a two cycle internal combustion engine. Thus as is shown in FIG. 1, gas or air supply 28 delivers pressured fluid to intake port 29 extending into chamber 20. Upon movement of the piston to the left as shown in FIG. 1, sensing means 30 which is responsive to the approach of the piston actuates combustion means 31. Thus where air supply 28 delivers a combustible fluid mixture, such as a fuel-air mixture, combustion means 31 comprises an ignition device. Similarly, combustion means 31 can include a fuel injector and ignition provisions for firing the charge or a fuel injector alone where the pressure within the chamber is sufficiently high to cause self-ignition.

In response to the combustion adjacent end portion- 20b of the chamber, piston 21 is moved to the right as shown in FIG. 1, thereby compressing and pumping the oil from pump chamber 23. As the piston moves to the right, fluid such as air within end portion 20a of the chamber is compressed and urges the piston in the direction opposite to its motion. As the piston continues to move to the right the pressured fluid within the chamber expands until exhaust port 32 is uncovered by piston 21 and serves as the means for releasing the fluid applied to the piston from the chamber. At this point the release of the pressured fluid from the chamber results in an unbalance of forces being applied to the piston since the fluid within end portion 20a is in a highly compressed state. Thus the fluid trapped under pressure in end portion 20a serves as a bounce chamber device to reverse the piston and return it toward end portion 20b of the chamber. As the exhaust fluid escapes from the chamber through port 32 a fresh charge of pressured fluid is introduced through port 29. Subsequently the return of the piston to the 'left, as shown in FIG. 1, causes the new charge 'to be compressed adjacent end portion 20b of the chamber and thereby prepares the engine for the next cycle of operation.

The arrangement by which a portion of the interior of the chamber surrounds pump piston 22 enables the engine to have a bouncechamber arrangement while at the same time being adapted to serve as a pump or to transmit mechanical motion by means of a stud or link inplace of the pump piston to an external load. I

It is to be further understood that a variety of fluid pressured devices are adapted to drive piston 21 such as the various types of Otto and diesel two cycle engine arrangements as well as valve schemes which are adapted to introduce into and subsequently to discharge from the chamber gas or liquid under pressure. In each case the prime mover for the piston is only required to drive it during the power stroke since the integral bounce chamber arrangement within chamber 20 is capable of restoring the piston to its starting point.

FIG. 2 shows two of the engine arrangements of FIG. 1 disposed in single chamber 33 to provide a horizontally opposed free piston type engine. Fluid supply 34 which can provide pressured fluid, pressured air or a fuel-air mixture to the chamber is connected to intake port 29. Sensing means 35a, each of which are shown schematically in FIG. 2, are responsive to the approach of pistons 21 to the central portion of the chamber by actuating combustion means 35. The combustion means can comprise an ignition or a fuel injection system. Upon combustion in central portion 33a of the chamber the pistons are urged by the pressured fluid in opposite directions. As the pistons approach end portions 33b and 330, the compression of a fluid within the end portion of the chamber, such as air, is capable of urging the pistons in the return direction toward the central portion of the chamber. Thus it can be seen that each of the pistons is adapted to transmit force to a load outside of the chamber and also to provide the means for urging the pistons in the return direction.

The free piston type device of FIG. 3 includes chamber 38 which contains free or engine piston 36 as well as additional piston 37 spaced apart therefrom. The space between the piston contains means for elastically transmitting at least a portion of the movement of the piston to one another, such as by a volume of air or other fluid. Thus a cushion of air between end portion 36a and end portion 37a of the pistons transmits the motion of one to the other. End portion 37b of the additional piston is exposed to end portion 38a of the chamber which contains an elastic cushion, such as that of a volume of air. The cushion provides the means for returning the additional piston as well as the engine piston during operation. From end portion 3711 pump piston 39 extends into pump chamber 23.

During operation combustion means 31 causes the application of pressured fluid to end portion 36b of the piston when it is adjacent end portion 38b of the chamber. The expansion of the fluid urges piston 36 to the right as shown in FIG. 3 and thereby applies compressive forces to the elastic cushion of air between the pistons. As the elastic cushion of air between the pistons contracts, it transmits the pressure to end 37a of the piston 37 which in turn applies force to the fluid in the pump chamber. Thus it can be seen that the motion of piston 36 is elasticallytransmitted to the additional piston.

Since the cushion of air between the pistons is compressible it enables a differential motion to occur between the piston and the additional piston. Thus for example, during high pressure levels within the chamber, greater contraction of the cushion between the pistons occurs. Under such a condition the motion of the additional piston can be less than that of the engine piston and therefore the displacement of fluid by the pump piston is reduced. On the contrary, for lower pressures within the pump chamber, the contraction of the cushion between the pistons is reduced and thus the additional piston can move substantially to the same extent as that of the engine piston. Here the displacement by the pump piston would approach the maximum. Thus it can be seen that the arrangement of the piston and additional piston with an elastic transmission means therebetween is capable of operating as a variable displacement pump or a device having a variable extent of output motion.

Of course after the power stroke of piston 36 and the corresponding movement in response thereto of additional piston 37, the forces of compression stored in end portion 38a of the chamber serve as the means for urging the additional piston and consequently the engine piston erationto'the additional piston which is connected to the pumping device. Thus the elasticity or resiliency of the cushion between the pistons is capable ofimproving the overall performance of the free engine type piston.

In order to balance the reactive forces experienced in the embodiment shown in FIG. 3, that is to achieve a balance of momentum, the assembly of FIG. 3 can be combined into. a horizontally opposed arrangement such as that shown in FIG. 4. Thus a pair of pistons 36 and additional pistons 37 are disposed within chamber 40. In response to the application of pressured fluid in the space between pistons as, the pistons are urged away i from one another, thereby causing the pistons to act upon the fluid or other elastic coupling or cushion between pistons 36 and additional pistons 37. Since the assemblies move in substantially equal amounts in opposite directions and with substantially equal and opposite velocities, a balance of momentum can be achieved. This results in the elimination of vibration and the need for restraint on the chamber. i

The arrangement shown in FIG. 5 is similar to the horizontally opposed arrangement of FIG. 4 with the exception that chamber 41 is divided by cylinder head 42 which forms separate chamber portions 41a and 41b. With this arrangement sensingmeans 43 extending into piston due to the expansion of the gas in the end portion of the chamber is elastically transmitted by means of the cushion of air or fluid between pistons 45 and additional piston 47. Movement of the additional piston results in a pumping action at relief 4-8 so that fluid is discharged through the outlet passageand check valve.

As fluid is discharged from one side of land 49 extending across relief 48, fluid is admitted to the other side. Additional piston 47 which is elastically coupled to adjacent piston 45 by a cushion of air or fluid results in the piston opposite the one being moved by pressured fluid to travel within the chamber as the additional piston is moved. In this way the piston is moved to the opposite end of the chamber Where it compresses a charge prior to the beginning of the next power cycle. 7 FIG. 8 shows means for applying pressured fluid to the free pistons in an engine of the type shown in FIG. 4 with the exception that chamber 64 includes intake port 65 and exhaust port 66, each disposed at a distance from the central portion of the chamber. Cams 57 and 63 are adapted to respond when pistons 36c and 36d, respectively, are at their innermost position adjacent the central portion of the chamber. The response of the cams is transmitted by linkage including pivoted levers 69 and links '70 coupled to combustion means '71. In turn the combustion means actuates device '72 which can be an ignition device or a fuel injection device.

During operation the movement of either piston to the innermost location actuates the cam related thereto which each of the chamber portions, actuate combustion means 44 which delivers a charge or initiates ignition in each of the chamberportions separated from one another. With the arrangement of FIG. -5 momentum.

can still be balanced even thoughthe chamber portions are isolated from one another. I I

In the engine-driven'pu'mpfof FIG. .6 free engine pistons 45 are disposed adjacent endportions 46a and .b of chamber 46. Adjacent central portions 460 of the chamber there is disposed additional piston 47 which 4h adjacent toports 5i and 51. Inlet'passages 52a.

and bha'vingchec'k valve 53a andb,'; respectively, are in communication with. ports '56. and 51. Ports Siland 51 alsoconnect to outlet passages 54 and 55, respectively, which contain check valves 56 and 57, respeck 'tively. Where. the pistons are to be driven by pressured fluid such as in a two cycle i engine arrangement, end portions 46a. and b of chamber .46 are provided with intake ports d and exhaust "ports 59. Source 60 'of pressu redjfluid "which-is connected to the intake ports can includea tuelair mixture. Onthe other hand fuel ""rnay, be delivered. to the' enlgine by'injectors 61 which are actuated by combustion means 62." Sensing means 63 extending into the end portions of the chamber rel'sured fuel-aiipmixture to the engine, combustion means 62 can actuate an ignition device in each of the end -port-ions of the chamber in placeof the fuel injectors.

spond to the approach o'f'pistons 45,, andin turn actuate combustion means '62. Where source 60 delivers a pres- Withthe arrangement shown in FIG. .6 fluid pressure 7 is applied alternately to diiferent ones of pistons 45.

one of the pistons toward the end portion of the chamber actuat-es combustion means 62' which ignites the mixture in the end portion. of thecharnber or injects fuel to initiate combustion. therein. The movementof the 7 0 Thus sensing means 63 in response to the approach of "said predetermined causes operation of the combustion means and thereby applies pressured fluid to the pistons which drive them in opposite directions. Since either cam can alone actuate the combustion me'ans, a transient out of phase condition of the pistons can be corrected. Regardless whether one of the pistons has not reached the innermost position when the other has, the combustion means fires the charge between the pistons and drives them inthe opposite direction with respect to one another. Consequently, the out of phase piston will be reversed before it has reached the innermost position and one or more cycles under such operation can restore the proper phasing of the pistons."

While- I have shown and described the preferred embodiments of the invention, it will be apparent that various modifications and changes may be made therein, particularly in the form and relation of the parts, without departing from the spirit of my invention'as set forth in the appended claims.

What is claimed:,

1. A free pistoii typ'e device comprising ,a-chamber, a piston disposed in said chamber, means for urging said piston to move from one extreme position thereof in a predetermined direction within said chamber toward the ,other extreme position thereof, an additional piston dis-. posed within said'chamber spaced apart in said predetermined direction from said piston, means permanently disposed in the space between said piston and said additional piston for elastically transmitting at least a portion of the movement of' said piston and said additional piston to one another, and means urging saidadditional piston in response to the movement thereof transmitted from' said piston for providing a restoring force suflicientto return said additional piston and thereby said piston opposite to direction toward said one extreme position.

=2. A free piston type device comprising a chamber, a piston disposed in said chamber, means for urging said piston to move from one extreme position thereof in a predetermined direction within said chamber toward the other extreme position thereof, an additional piston disposed within said chamber spaced apart in said predetermined direction from said piston, means permanently dis- "posed in the space between said piston and-said additional piston for elastically transmitting at leasta portion of the movement of said piston and said additional piston to one another, structure forming a bounce chamber in communication with the side of said additional piston disposed opposite to said piston for moving said additional piston and said piston opposite to said predetermined direction to return said additional piston and thereby said piston toward said one extreme position thereof, and means for transmitting the movement of said additional piston to a load.

3. A free piston type engine comprising a chamber, a piston disposed within said chamber, means for applying a pressured fluid to said piston to move said piston Within said chamber in a predetermined direction from one extreme position thereof toward said other extreme position thereof, means for releasing said fluid applied to said piston from said chamber after movement of said piston in said predetermined direction, an additional piston disposed in said chamber spaced apart in said predetermined direction from said piston, means permanently disposed in the space between said piston and said additional piston for elastically transmitting at least a portion of the movement of said piston and said additional piston to one another, and structure forming a bounce chamber in communication with the side of said additional piston disposed opposite to said piston for moving said additional piston and said piston opposite to said predetermined direction to return said additional piston and thereby said piston toward said one extreme position thereof.

4. A free piston type device comprising a chamber, a piston disposed in said chamber, means for urging said piston to move from one extreme position thereof in a predetermined direction within said chamber toward the other extreme position thereof, an additional piston disposed within said chamber spaced apart in said predetermined direction from said piston, means permanently disposed in the space between said piston and said additional piston for elastically transmitting at least a portion of the movement of said piston and said additional piston to one another, structure forming a bounce chamber in communication with the side of said additional piston disposed opposite to said piston for moving said additional piston and said piston opposite to said predetermined direction to return said additional piston and thereby said piston toward said one extreme position thereof, and means actuated by said additional piston for pumping a fluid.

5. A free piston type device comprising a pair of chambers each mechanically coupled to and extending in opposite directions from one another, a piston disposed in each of said chambers, means for urging said pistons to move in opposite predetermined directions within said chambers, an additional piston disposed in each of said chambers spaced apart in said predetermined direction from said piston therein, means permanently disposed in the space in each chamber between said piston and said additional piston therein for elastically transmitting at least a portion of the movement of said piston and said additional piston to one another, and means urging each of said additional pistons for moving said additional'piston and said piston within its chamber opposite to the predetermined direction in which the piston therein is urged.

6. A free piston type device comprising a pair of chambers each mechanically coupled to and extending in opposite directions from one another, a piston disposed in each of said chambers, means for urging each of said pistons to move in opposite predetermined directions within said chambers, an additional piston disposed in each of said chambers spaced apart in said predetermined direction from said piston therein, means permanently disposed in the space in each chamber between said piston and said additional piston therein for elastically transmitting at least a portion of the movement of said piston and said additional piston to one another, means urging each of said additional pistons for moving said additional piston and said piston Within its chamber opposite to the pre- -determined direction of the piston therein, and means for transmitting the movement of each of said additional pistons to a load.

7. A free piston type device comprising a chamber, a pair of pistons disposed spaced apart from one another in said chamber, means for urging said pistons to move from one extreme position of each of said pistons in opposite predetermined directions within said chamber toward the end portions thereof and the other extreme position of each of said pistons, an additional piston disposed in said chamber between each of said pistons and the end portion of said chamber adjacent thereto, means permanently disposed in the space in each chamber between each piston and said additional piston adjacent thereto for elastically transmitting at least a portion of the movement of each of said pistons and said additional piston adjacent thereto to one another, and means urging each of said additional pistons in response to the movement thereof transmitted from said piston adjacent thereto for providing a restoring force suificient to return each of said additional pistons and thereby said pistons adjacent thereto within said chamber opposite to said predetermined directions toward said one extreme position of each of said pistons.

8. A free piston type device comprising a chamber, a pair of pistons disposed spaced apart from one another in said chamber, means for urging each of said pistons to move from one extreme position of each of said pistons in opposite predetermined directions within said chamber toward the end portions thereof and the other extreme position of each of said pistons, an additional piston disposed in said chamber between each of said pistons and the end portion of said chamber adjacent thereto, means permanently disposed in the space in each chamber between each piston and said additional piston adjacent thereto for elastically transmitting at least a portion of the movement of each of said pistons and said additional piston adjacent thereto to one another, structure forming a bounce chamber in communication with the side of each of said additional piston disposed opposite to said piston adjacent thereto for within said chamber opposite to said predetermined directions to return said additional pistons and thereby said pistons toward said one extreme position of each of said pistons, and means for transmitting the movement of each of said additional pistons to a load.

9. A free piston type device comprising a chamber, a pair of pistons disposed in said chamber spaced apart from one another, each piston of said pair being adjacent a different end portion of said chamber, an additional piston disposed in the space in said chamber between said pair of pistons, means operable within said end portions for alternately urging a different one of said pair of pistons to move within said chamber toward said additional piston, means disposed between each piston and the adjacent end portion of said additional piston for transmitting at least a portion of the movement of said pistons and said additional piston to one another, and means within said end portions for alternately urging the remaining one of said pair of pistons to oppose the movement of said additional piston.

10. A free piston type device comprising a chamber, a pair of pistons disposed in said chamber spaced apart from one another, each piston of said pair being adjacent a different end portion of said chamber, an additional piston disposed in the space in said chamber between said pair of pistons, means operable within said end portions for alternately urging a different one of said pair of pistons to move within said chamber toward said additional piston, means disposed between each piston and the adjacent end portion of said additional piston for transmitting at least a portion of the movement of said pistons and said additional piston to one another, means Within said end portions for alternately urging the remaining one of said pair of pistons to oppose the movement of said additional piston, and means actuated by said additional piston for pumping a fluid.

11. A free piston type device comprising a chamber,

a pair of pistons disposed in said chamber spaced apart from one another, each piston of said pair being adjacent a different end portion of said chamber, an additional piston disposed in the space in said chamber between said pair of pistons, means operable Within said end portions for alternately urging a diflerent one of said pair of pistons to move within said chamber toward said additional piston, a fluid cushion between each piston and the adjacent end portion of said additional piston for transmitting at least a portion of the movement of said pistons and said additional'piston to one another, and means within said end portions for alternately urging the remaining one of said pair ofpistons to oppose the movement of said additional piston.

12. A tree piston type device comprising a chamber, a pair of pistons disposed in said chamber spaced apart from one another, each piston of said pair being adjacent a different end portion of said chamber, an additional pistondisposed in the space in said chamber between said pair of pistons, means operable within said end portionsi for alternately urging a diiferent one of said pair ofpistons to move within said chamber toward'said additional piston, means disposed betweeneach piston a pressured fluid between said pistons to move said pistons from one extreme position of each of said pistons in predetermined opposite directions toward the other extreme position of each of said pistons, means disposed between said central portion and the other end portion of said chamber for releasing said fluid after movement of said pistons in opposite directions, an additional piston adjacent thereto to oneanother, and structure forming":

a bounce chamber in communication with the side of each of said additional piston disposed opposite to said piston adjacent thereto for urging each of said additional pistons to move within said chamber opposite to said' predetermined directions to return said additional pistons and thereby said pistons toward'said one "extreme position of each of said pistons. i

r 15. A free piston type device comprising a chamber, a pair of pistons disposed spaced apartfrorn one another in said chamber, means disposed between thecentral and the adjacent end portionviof said additional piston v for elastically transmitting at least a portion'of the movement of said pistons and said additional piston to one another, said additional piston including means for pumping a fluid'with respect to said chamber in responsev to the 'movementof said additional piston, and means apart from one another, each :piston of saidpair being adjacent-a different ,end portion of said, chamber, an" additional piston disposed. in thespace in said chamber between said pair of pistons means operable within said end portions for alternately urging a different one of said pair of pistons to move within said chamber toward said additional piston, .means disposed between each piston and the adjacent end portion of said-additional piston for transmitting at least a portion 'of. the movernent of said pistons and'saidaddition'al piston to one another, said additional" piston having a; means for pumping fluid with respect to} said ports, and means Within said end portions for,'alternatelyufging' the remaining'one of said pair of pistons toroppose the m vement of said additional piston. r

14. A free piston type device comprising a,cham'ber,

-a pair of pistons disposed spacedaparttrom one another in said' chamber,"means disposed between the central portion and-one end portion of; said chamber ,for applying portion and one end portion of said chamber for applying a pressured fluid between said pistons to move said pistons from one extreme position of each of said pistons in predetermined opposite directions 'toward the other extreme position of each of said pistons, means disposed between said central portion and the other end' portion of said chamber forreleasing' said fluid aftermovement of said pistons in opposite directions, an'addition'al piston r disposed in said chamber between each vof said pistons and the end portion of said chamber adjacent thereto," I means disposed in the space in each chamber between each piston and saidadditi'onalpiston adjacent thereto for elastically transmitting at least a portion'jof the move, mentlo'f each of said pistons and saidadditional piston adjacent thereto to one another, structure forming a bounce chamber in communication with the side of each a of said additional'pistonldisposed*opposite to said piston} adjacent thereto for urging each of said additional pistons 1 to move within said chamber opposite'tosaid predetermined directions to return said additionahpistons and i thereby said'pistons toward said one'extreme position-of each of said pistons, andf means fortr'ansmitting the 7' i movement of each of said additional pistonsto a" load.

. lytereiices Cited by the Examiner- UNITED STATES PArnrrrs W i; 6 H a 103-44 Z C V E NER; imai'y'ExaminefQ i R B T q i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 170,406 February 23, 1965 Raymond A. Robertson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 18, for "aditional" read additional column 3, line 4, for "move" read moves column 4, line 29, for "piston" read pistons column 5, line 41, for "portions" read portion column 8, line 40, after "for" insert moving each of said additional pistons and said piston adjacent thereto (SEAL) Attest:

ERNEST W. SWIDER' Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A FREE PISTON TYPE DEVICE COMPRISING A CHAMBER, A PISTON DISPOSED IN SAID CHAMBER, MEANS FOR URGING SAID PISTON TO MOVE FROM ONE EXTREME POSITION THEREOF IN A PREDETERMINED DIRECTION WITHIN SAID CHAMBER TOWARD THE OTHER EXTREME POSITION THEREOF, AN ADDITIONAL PISTON DISPOSED WITHIN SAID CHAMBER SPACED APART IN SAID PREDETERMINED DIRECTION FROM SAID PISTON, MEANS PERMANENTLY DISPOSED IN THE SPACE BETWEEN SAID PISTON AND SAID ADDITIONAL PISTON FOR ELASTICALLY TRANSMITTING AT LEAST A PORTION OF THE MOVEMENT OF SAID PISTON AND SAID ADDITIONAL PISTON TO ONE ANOTHER, AND MEANS URGING SAID ADDITIONAL PISTON IN RESPONSE TO THE MOVEMENT THEREOF TRANSMITTED FROM SAID PISTON FOR PROVIDING A RESTORING FORCE SUFFICIENT TO RETURN SAID ADDITIONAL PISTON AND THEREBY SAID PISTON OPPOSITE TO SAID PREDETERMINED DIRECTION TOWARD SAID ONE EXTREME POSITION. 